1. Field of the Invention
The present invention relates generally to systems for transferring particulate materials, and, more particularly, but not by way of limitation, to systems for transferring particulate material, such as coal from railroad cars into an underground storage bunker, while maintaining the particulate matter in a substantially covered or protected condition.
2. Description of the Prior Art
In prior art systems, the material is not covered substantially continuously during an unloading operation. Thus, the particulate material is exposed to moisture or water (in the form of rain, snow, and the like) or blowing dust and debris. This is particularly undesirable when the particulate matter being transferred is in a dried or purified form.
In the past, some drop-bottom railroad cars were constructed having downwardly swinging doors. Such devices are disclosed in U.S. Pat. Nos. 2,399,708, issued to H. W. Sanford, and 2,487,447, issued to R. C. Kepner. In the prior art systems, as set forth above, the mechanisms utilized to unlatch and relatch the downwardly swinging doors were positioned between the track rails above a storage bunker. Thus, as the railroad car was moved over the storage bunker, the unlatching mechanism was engaged by the door latch, thereby allowing the door to swing downwardly. The material was then delivered from the railroad car through the opened bottom-drop door. To relatch the doors, each car had to be moved in a reverse direction over the relatching mechanism.
Other unloading systems are disclosed in U.S. Pat. Nos. 3,227,110, issued to J. T. Smith, et al.; 3,543,691, issued to Ernest J. Nagy; and 3,633,772, issued to Roy W. Miller. In general, the systems disclosed in such patents permit the railroad cars to be moved over the length of a storage bunker without the necessity of moving each car in the reverse direction over a relatching mechanism. Such systems utilized cam tracks positioned between or near the side of the track rails and compatible cam followers connected to the drop-bottom doors on each railroad car.